1. Technical Field
The present invention relates to a technical field of an electro-optical device substrate used for an electro-optical device, such as a liquid crystal device, an electro-optical device that is provided with the electro-optical device substrate, and an electronic apparatus, such as a liquid crystal projector, that is provided with the electro-optical device.
2. Related Art
A liquid crystal device, which is an example of the above electro-optical device, is not only used for a direct view type display but also used widely, for example, as a light modulating device (light valve) of a projection-type display device. Particularly, when in a projection-type display device, because intensive light emitted from a light source enters a liquid crystal light valve, a light shielding film, which serves as a light shielding device that blocks incident light, is installed in the liquid crystal light valve so that a thin-film transistor (TFT) in the liquid crystal light valve does not cause an increase in leakage current and/or a malfunction, or the like, because of the intensive light. In regard to the above light shielding device or the light shielding film, JP-A-2004-4722 describes a technology for blocking light using a scanning line, which serves as a gate electrode, in a channel region of a TFT. Japanese Patent No. 3,731,447 describes that light that reaches the channel region of a TFT is reduced by providing a plurality of light shielding films formed on the channel region and a layer that absorbs internally reflected light. JP-A-2003-262888 describes a technology for reducing incident light that enters the channel region of a TFT as much as possible while making it possible to ensure an appropriate operation of the TFT and to reduce the width of a scanning line.
On the other hand, in the electro-optical device of such type, a holding capacitor is provided in a region in which a light shielding film is formed on a substrate, that is, in a region that does not allow transmission of light on the substrate, to hold the electric potential of a pixel electrode for a certain period of time by temporarily holding an image signal supplied to the pixel electrode. The above holding capacitor has an electrode, which is a component of the holding capacitor, that also serves as a light shielding film, so that the holding capacitor is able to shield a TFT against light.
However, when light is irradiated to a junction region of, for example, an LDD (Lightly Doped Drain) region, or the like, formed between a channel region and a source/drain region, there is a technical problem in which a light leakage current may be generated in the junction region. To address the above problem, it is conceivable that a light shielding device is provided on or above junction regions formed on both sides of the channel region. However, in terms of display performance, it is not preferable to reduce an aperture region through which light is substantially transmitted in each pixel. On the other hand, when light is irradiated to the junction region formed between the channel region and the source/drain region that is connected to a pixel electrode, in comparison with the case where light is irradiated to the junction region formed between the channel region and the source/drain region that is connected to a data line, the inventors of the invention estimate that a light leakage current is more likely to be generated in the TFT.
In addition, when the pattern of the light shielding film that shields semiconductor elements, such as pixel switching TFTs, is changed in order to reduce a light leakage current, there is a technical problem that it leads to a decrease in aperture ratio in each pixel or a decrease in contrast of an display image and, hence, the display performance of an electro-optical device is deteriorated.
On the other hand, in the electro-optical device of this type, there is a need for reducing a pitch at which pixels are arranged in order to reduce the size of the device and to realize a high-resolution display image.
Furthermore, to realize a high-quality image display, it is preferable that there is no variation in display characteristic among pixels.